I've used tungsten rod, for EDM'ing narrow holes (0.040"), in boron carbide. By tungsten,
I mean the soft tungsten metal, available as wire, not tungsten carbide. Kerosene bath
with a pump to flush the cut (Shell Diala AX specifically, but it sure looked like kerosene).
We used an aircraft 28V oil pump, but I see lots of 12v diesel/fuel pumps for automotive
use that would probably circulate fluid just fine.
I recall some cuts worked best with the wire probing UP into the work.
What I do NOT recall, is if the whole apparatus cranked up from the coolant tank, or whether
the tank dropped down to set up the tooling and workpiece.